The present invention relates to a scroll-type fluid machine which is constructed by combining an orbiting scroll and a fixed scroll.
Air conditioning units have recently used a scroll-type compressor (scroll-type fluid machine) because of its advantage of efficient compression.
As shown in FIGS. 6 and 7 the scroll-type compressor is constructed so as to have a scroll-type compressor section h which combines a fixed scroll d including a spiral wrap b disposed on an end plate a and a peripheral wall surrounding the wrap b with orbiting scroll g including a spiral wrap f disposed on an end plate e.
Specifically, the compressor section h combines the scrolls d and g so that they engage with each other at a predetermined shifted angle to define enclosed spaces i for producing compression between these wraps.
The volume of the enclosed space i decreases gradually from the peripheral side to the center by revolving the orbiting scroll g around the axis of the fixed scroll d using, for example, a rotating shaft k having an eccentric pin j at its tip. That is to say, the compressor section h compresses a gas by taking advantage of the change in its volume. The orbiting scroll g is provided with a rotation checking mechanism, such as an Oldham's ring, for checking the rotation of the orbiting scroll g, though not shown in the figure.
With such a scroll-type compressor, to prevent gas leakage from the enclosed space i, the fixed scroll d is supported in such a manner as to be displaced in the axial direction, and back pressure chambers m are disposed on the back surface side of the fixed scroll d as shown in FIG. 6, so that the fixed scroll d is pressed against the orbiting scroll g in the axial direction. Alternatively, a back pressure chamber (not shown) is disposed on the back surface side of the orbiting scroll g, so that the orbiting scroll g is inversely pressed against the fixed scroll d in the axial direction.
The scroll-type compressor has a disadvantage that the peripheral portion of the end plate e of the orbiting scroll g and the axial end surface of the peripheral wall c of the fixed scroll d are worn because these portions are pressed against each other during the operation by a force which revolves the orbiting scroll g in the reverse direction.
Therefore, consideration has been made to prevent the wear by embedding a hard, wear-resistant plate n at the periphery of the orbiting scroll g, which is slidingly in contact with the axial end surface of the peripheral wall c of the fixed scroll d, using the techniques disclosed in Japanese Patent Laid-Open No. S55-72680 and Japanese Patent Laid-Open No. H2-298686.
Specifically, as shown in FIG. 8, a continuous, annular groove o is formed in the circumferential direction at the periphery of the orbiting scroll g, which is slidingly in contact with the axial end surface of the peripheral wall c, and a hard, wear-resistant plate n, which is formed into a ring shape, is embedded in the groove o.
This construction, in which the wear-resistant plate n is separately installed, produces a difference in level .delta. between the axial end surface of the wear-resistant plate n and the axial end surface of the end plate e of the orbiting scroll g as shown in FIG. 8.
It has been found that this difference in level .delta. reduces the compressibility of the scroll-type compressor or accelerates wear of the wear-resistant plate n and the end plate e.
However, the tolerance which avoids the problem caused by this difference in level .delta. has not been established; therefore, the problem has not been solved.